1. Field of the Invention
The present invention relates generally to instant filmstrips, also called self-developing filmstrips. More particularly it relates to instant filmstrips adapted for use in conventional cameras and for providing prompt development of the filmstrip at the photographic site.
2. Description of the Prior Art
Cameras for receiving film packs and individual film units to produce instant photographic prints are commercially available, and cameras for use with self-developing film assemblies to produce instant photographic transparencies are well known in the art. Generally, the latter cameras include special apparatus for effecting rapid processing, such as described in U.S. Pat. No. 3,350,990 entitled "Camera Apparatus" by P. Finelli, issued Nov. 7, 1967. The film assemblies used in these cameras are not suitable for use in conventional cameras.
Still other self-developing type film assemblies are known which are adapted for exposure of the film in conventional, commercially available cameras. For example, U.S. Pat. No. 4,145,133 entitled "Film Assemblage of the Self-Developing Type Together With Apparatus for Processing Thereof" by R. R. Wareham, issued Mar. 20, 1979, and U.S. Pat. No. 4,200,383 entitled "Transparency Film Processor" by L. V. Bendoni et al, issued Apr. 29, 1980, disclose film assemblies adapted for exposure in conventional 35 mm cameras and for development in special processors which are portable enough to carry to the photographic site.
The film assembly disclosed in the Wareham patent includes an elongated filmstrip having two superposed sheets coated with photographic material helically wound in a cartridge with a pod of processing composition. A strip of heat-activated adhesive is disposed along each lateral edge of the filmstrip between the superposed sheets. After exposure, the entire filmstrip, including the pod, is withdrawn from the cartridge and loaded into a special processor. In the processor, the adhesive is heated to seal the edges of the sheets together, and the filmstrip is run between pressure rollers to break the pod and spread the processing composition between the sealed sheets.
The step of heat-sealing the lateral edges of the Wareham assembly effectively rules out the possibility of in-camera processing in conventional cameras not provided with heat-sealing apparatus. The film assembly disclosed in the Bendoni et al patent does not employ heat-activated adhesive to seal the filmstrip edges. Instead, a pair of spaced apart rails between the two superposed photographic material sheets cooperate with ribs in a special processor for inhibiting leakage of processing composition.